The present invention relates to an optical apparatus including an image stabilization system for suppressing an image shake. An optical apparatus such as binoculars, an image pickup apparatus, and an interchangeable lens includes an image stabilization system that detects a shake such as a hand shake by a shake sensor such as a gyro sensor and drives an optical element such as a lens so as to suppress an image shake based on the output from the shake sensor. Some image stabilization systems have the function to stop the image stabilizing operation by operating the image stabilization switch again after starting the image stabilizing operation in accordance with the operation of the image stabilization switch.
However, if the optical apparatus is not used to observe or image but continues to be just carried for a long time, the image stabilization system consumes a wasted power since the image stabilization system continues to operate in the meantime.
Therefore, the image stabilization system often has an energy-saving function in which the operation automatically stops or is changed to standby mode in accordance with the elapse of a predetermined time after the image stabilization system starts to operate.
FIG. 8 shows an energy-saving function of the image stabilization system. When an image stabilization switch (IS-SW) 81 is turned on at timing 81a, the system changes to an IS mode 82 (82a) for performing an image stabilizing operation. When the image stabilization switch 81 is turned off in the IS mode 82, the system switches from the IS mode 82 to a standby mode 83 (83a).
The standby mode means a condition in which the power supply to the drive circuit that moves an optical element is cut off with maintaining the power supply to the shake sensor. In case that the power supply is cut off, the shake sensor such as a gyro sensor needs a long time until the operation is stable even if the power supply resumes. This is because of an initial unstable factor of the sensor itself, and because of a charge time of a capacitor due to time constant of a high-pass filter or an integrator.
Therefore, for example Japanese Patent Laid-Open No. 7-199122 discloses an optical apparatus that is capable of resuming a stable operation of an image stabilization system in short time while reducing power consumption, by providing a standby mode that continues the power supply to a shake sensor even if the power supply to the drive circuit is cut off.
When the image stabilization switch 81 is turned on at timing 81c, the system performs the image stabilizing operation by changing to the IS mode 82. However, when a predetermined time (hereinafter referred to as IS time, for example 5 minutes) has elapsed, the system changes from the IS mode 82 to the standby mode 83 (83b).
In the standby mode 83, the predetermined time (hereinafter referred to as standby time, for example 3 minutes) has elapsed, the power supply to the system (other than the drive circuit including the shake sensor) is cuts off.
The optical apparatus as described above often uses a battery as a power source. The power of the battery can be used in the condition of the standby mode as well as the condition of the IS mode. Furthermore, when the remaining amount of the battery (voltage) decreases, wasting of the battery is faster since a current increases and an internal resistance also increases.
However, in a conventional image stabilization system, the IS time or the standby time is fixed regardless of a remaining amount of the battery. Therefore, in the condition where the remaining amount of the battery is particularly small, there is a possibility that wasted power is consumed more than in the condition where the remaining amount is enough.